Neural stem cells (NSC's) provide great promise for cell-based therapies for diseases of aging, such as Alzheimer's disease, because they self-renew and form the three main cell types of the central nervous system: neurons, astrocytes, and oligodendrocytes. A basic understanding of the molecular mechanisms that control the proliferation and differentiation of these cells will greatly aid their therapeutic potential. One molecular mechanism implicated in these processes involves the activity of the LIM homeodomain transcription factor Lhx2, since Lhx2 knockout mice are unable to form a cerebral cortex during development. This finding suggests that Lhx2 is a critical regulator of the NSCs that generate the differentiated cells of the cortex. In preliminary data we show that NSCs isolated from Lhx2 knockout mice are deficient in proliferation compared to cells from littermate controls. Differentiation of Lhx2 knockout NSCs reveals that they produce fewer neurons with shorter neurites (dendrites and axons) than cells from control mice. Lhx2 is expressed in NSC-rich regions of the developing primate brain and the human Lhx2 sequence is 99% identical to the mouse, suggesting that Lhx2 performs similar functions in humans and mice. The specific aims of this proposal will test the following hypotheses: (1) Lhx2 regulates proliferation of mouse NSCs, (2) Lhx2 directs neuronal specification and neurite outgrowth of mouse NSCs, and (3) Lhx2 plays similar roles in the proliferation and differentiation of human NSCs. The overall goal of this proposal is to clarify the role of Lhx2 in NSC proliferation, neuronal specification, and neurite outgrowth in mice and humans with the eventual goal of using this information to aid cell-based therapeutics for neurological diseases of aging. Dr. Lisa Flanagan, Ph.D., earned her doctoral degree in neuroscience studying molecular mechanisms of Alzheimer's disease. She subsequently explored basic cell biology and the cytoskeleton and is now combining these areas of expertise in the study of NSCs. Dr. Flanagan's goal is to establish an independent research program to investigate the regulation of NSCs, and she will receive additional training through this award toward this goal by her interaction with mentors, collaborators, and laboratory coursework. She is pursuing her research at UC Irvine, which has outstanding resources that will aid her in her career development and goals.